Composite concrete

ABSTRACT

An ultra-high performance composite concrete, with low cement and fiber content and having good mechanical properties as well as good impacts, shocks and projectile protection properties, includes hydraulic binder, aggregates, an admixture of metal fibers. Particularly, the composite concrete includes 70% to 85% of particles (A) having a particle size distribution which ranges from 0.01 to 3 mm up to particle size distribution which ranges from 0.01 to 0.50 mm; 2% to 10% of particles (B) having particle size of between 0.01 and 1 μm; 3% to 20% of hydraulic binder; 0.1 to 3% of a dispersant or plasticizer; 0.05% to 8.5% of fibers; and, mixing water, wherein the percentages being weight percentages based on the sum of the weights of constituents a) to d).

The invention relates to a composite concrete with a low cement andfibres content having good mechanical properties, and also possessinggood impacts, shocks and projectiles protection properties.

PRIOR ART

In January 1990, the publication of the French Patent Application No.2,633,922 disclosed a compacted concrete comprising:

a) 7 to 15% by weight of a cement or of a binder for road,

b) 4 to 7% of water,

c) 0.8 to 4% by weight of metal fibres, the balance consisting of

d) 70.7 to 87.8% of granular material with a particle size of from 0 to31.5 mm,

e) where appropriate, 0.05 to 2% by weight with respect to the cement,of concretes admixtures, and

f) where appropriate, 5 to 20% by weight with respect to the cement, offly ashes or of ultrafines.

This concrete must be compacted in order to reach its maximum mechanicalproperties. However, despite the compacting operation, it still hasrelatively low mechanical properties. This is why it is difficult tofind applications for it other than as industrial slabs, roadways,aircraft runways, platforms and roadsides.

In June 1990, French Patent Application No. 2,640,962 proposed acomposite concrete comprising, in parts by weight per 100 parts ofhydraulic binder:

a hydraulic binder composed of cement (100 parts);

aggregates of high hardness and of particulate geometry, either round orangular (120 to 200 parts);

aggregates of high fineness (40 to 65 parts);

microsilica (3 to 15 parts);

water (25 to 35 parts).

Moreover, this composite concrete having a relatively high cement andfibres content is reputed to be capable of limiting the penetration ofprojectiles. However, this property is neither demonstrated norillustrated.

DE-A-3,734,327 describes a structural element capable of withstandingthe penetration of projectiles. These elements are produced by means ofa composite concrete comprising a hydraulic binder composed of a cement(Z35 to 55:270 to 450 kg/m³), hard additives (basalt, quartz orquartzite, either by themselves or mixed) having a size of at least 4mm, silica powder (1850 to 1500 kg/m³) and fibres (steel, glass,synthetic, and carbon fibres).

Since this concrete contains no dispersing agent or plasticizer, themixing-water content is, in a known manner, generally greater than 30%by weight, leading to slight mechanical properties, in particular withregard to the compression strength and flexural strength, and moreparticularly with regard to the depth of penetration of projectileswhich cannot be other than important. These mechanical properties are,however, neither demonstrated nor illustrated in the description.

U.S. Pat. No. 4,472,201 proposes a composite concrete, having good heatstability, for a different field of application, which contains:

from 5 to 70 parts by weight of a mixture comprising:

49.95 to 87.3% by weight of a hydraulic cement,

49.95 to 9.7% by weight of an amorphous silica, and

0.1 to 3% by weight of a dispersing agent,

and from 95 to 30 parts by weight of a refractory aggregate.

This concrete may also include metal fibres, glass fibres, ceramicfibres, carbon fibres, alumina fibres or other types of fibres.

However, this composite concrete contains a large amount of mixingwater, leading to slight mechanical properties, in particular for thecompression strength and flexural strength, which would lead, ipsofacto, to a significant depth of penetration of projectiles in the caseof this composition being used for protection.

All the prior art (and especially FR-A-2,633,922) shows that there is atechnical prejudice which considers that, compared to conventional castconcretes, only concretes requiring compaction have a lower watercontent.

There therefore has not existed, until now, a concrete which could becasted or intended to be compacted having both good mechanicalproperties while still having a low cement, fibres and water content.This concrete would additionally be advantageous if it also possessedgood impact, shock and projectile protection properties.

BRIEF DESCRIPTION OF THE INVENTION

The Applicant has therefore managed to fill the gap mentioned above bydeveloping a composite concrete of the type comprising a hydraulicbinder, aggregates, an admixture, fibres and mixing water, characterizedin that it comprises:

a) from 70 to 85% of particles (A) having a particle size distributionwhich may range from 0.01 to 3 mm up to 0.01 to 50 mm,

b) from 2 to 10% of particles (B) having a particle size of between 0.01and 1 μm, i.e. between 10⁻⁵ and 10⁻³ μm,

c) from 0 to 12% of particles (C) of which at least a majority have aparticle size of between 1 and 10 μm, i.e. between 10⁻³ and 10⁻² μm,

d) from 3 to 20% of hydraulic binder,

e) from 0.1 to 3% of a dispersant or of a plasticizer,

f) from 0.05 to 8.5% of fibres, and

g) from 2 to 4.2% of water,

the percentages all being percentages by weight relative to the sum ofthe weights of constituents a) to e).

This concrete therefore offers at least the following advantages:

a low cement content,

a low fibres content,

simple implementation,

good mechanical properties,

good impacts, shocks or projectiles protection properties.

Further advantages of this concrete will appear on reading thedescription below.

DETAILED DESCRIPTION OF THE INVENTION

The particles (A) of the concrete according to the invention have aparticle size distribution which may range from 0.01 to 3 mm up to 0.01to 50 mm. These particles are aggregates, granulates or gravels whichgenerally have highly irregular and varied shapes. They may consist, forexample, of one or more materials, such as tabular-form alumina,electrofused corundum, natural or calcined bauxite, alumina-basedmaterials sold under the trademark "ALAG", granite, quartzite, diabase,basalt, crystalline quartz, silicon carbides, silicon nitrides, boroncarbides, titanium carbides, metals, metal alloys, etc. It is preferredto choose aggregates having a hardness greater than 5 Mohs.

At least a majority of particles (B) have a particle size of between0.01 and 1 μm. These are fly ashes or various ultra-fine fillers such assilica fumes, microsilicas, kaolinites, calcined clays, limestone fines,chromium oxide, titanium oxide, zirconium oxide, aluminium oxide, etc.They are obtained, for example, by condensation or precipitation.

Preferably, silica fumes such as for example those sold by the Elkemcompany under the name 971 U, is used as particles (B).

The hydraulic binder is preferably an alumina cement, a mixture ofalumina cements, a vitreous cement or a mixture of vitreous cements, aPortland cement whether composed or not (CEM I, CEM II) or a mixture ofPortland cements, a cement containing slag or pozzolane.

It is also conceivable to use a mixture of at least one alumina orvitreous cement with at least one Portland cement or a cement containingslag or pozzolanes. However in this case, it is necessary for thoseskilled in the art to take additional and well-known precautions tomaintain workability of concrete and to adjust its setting time. Suchprecautions may consist, for example in adding a set-retarder, plaster,etc.

The fibre content present in the concrete according to the invention ispreferably between 0.05% and 5% by weight.

As dispersing agent or plasticizer, it is possible to use, for example,a hexametaphosphate, a tripolyphosphate, a polynaphthalene sulphonate, asulphonated polyamine, etc. The mentioned percentages (0.1 to 3%)correspond to the weight of dry matter in relation to the sum of theweights of constituents a) to e).

The concrete according to the invention may also contain particles (C)of which at least a majority have a particle size of between 1 and 10μm. These are fine fillers preferably in the form of particles havinggenerally spherical geometry. They may be obtained, for example bygrinding by means of a ball mill. They may consist, for example oftabular-form alumina, electrofused corundum, natural or calcinedbauxite, alumina-based materials sold under the trademark "ALAG",granite, limestone, quartzite, diabase, basalt, ground crystallinequartz, silicon carbides, silicon nitrides, boron carbides, titaniumcarbides, metals, metal alloys, etc.

The use of particles (C) is preferable when the amount of hydraulicbinder employed is low.

The particle (C) content is preferably less than 12% by weight withrespect to the sum of the weights of constituents a) to e) and thepercentage of fibres is calculated by weight with respect to the sum ofthe weights of constituents a) to e).

The concrete according to the invention may furthermore contain one ormore admixtures of various kinds, such as, for example an anti-foamagent, a water-proofing agent, an air entrainer, a set-accelerator, aset-retarder, a colorant, etc. The admixture(s) content is generallyless than 1% by weight with respect to the sum of the weights ofconstituents a) to e) of the concrete.

The Applicant has discovered that it is desirable for the compactness ofthe concrete to be at maximum. This may be achieved, for example, byensuring that the distribution curves (number of particles as a functionof their size) of particles (A), of particles (B), of particlesconstitutive of the hydraulic binder and, where appropriate of particles(C) are continuous or have the continuity maximum, it being understoodthat the medium does indeed contain the dispersing agent or plasticizer.Thus, the concrete according to the invention contains particles (A) and(B) having the highest possible number of different sizes within therange corresponding to them, namely from 0.01 mm to 50 mm and from 0.01to 1 μm respectively thereby enabling it to have the maximum compactnessand giving it optimum mechanical and penetration resistance properties.

During preparation of the concrete according to the invention, itsvarious constituents are mixed in the presence of water. This water isessential for hydrating the hydraulic binder. The amount of waterinvolved depends on the fluidity and workability which it is desired toobtain for casting the concrete. It is generally between 2 and 5% byweight with respect to the sum of the weights of constituents a) to e)of the concrete. The water is generally introduced before the fibres.

After water and fibre addition, homogenization by mixing or blending andpouring into place, it is advantageous for the concrete to undergo aperiod of cure, preferably in a humid atmosphere. Next, it is desirableto subject the concrete to an heat treatment under controlledatmosphere. This heat treatment under controlled atmosphere may takeplace at a temperature of between 80° C. and 600° C., preferably between110° C. and 350° C. Of course, the heat-treatment under controlledatmosphere temperature is chosen taking into account the nature of thefibres, so as not to damage them.

A concrete is thus obtained which possesses good mechanical properties,although it has been prepared in a relatively simple manner, has a lowcement content and has not undergone a compacting operation.

The impact or shock resistance properties are manifested by an abilityto resist fracture or shattering under impact or shock.

The projectile resistance properties are manifested by an ability toslow and stop the penetration of this projectile and to resist fractureor shattering under impact of projectile. In other words, a concretepossessing good projectile protection properties is a concrete which hasa projectile penetration resistance sufficiently high for the depth ofpenetration of this projectile to be small and which, furthermore doesnot break under impact of projectile.

The concrete according to the invention therefore enables to reachimportant impact, shock or projectile protection even when it isemployed in the form of thin slabs, walls or partitions.

It may therefore be employed for providing coatings for protectionagainst small size projectiles, such as bullets fired by firearms, oragainst large projectiles, such as bombs.

It may also serve for manufacturing personal or collective shelters,whether static or mobile, for the protection of banks, prisons andso-called vital industrial installations, against intrusions or attackwhich could be committed, in particular using pick hammers or similartools, or for coating objects which have to be transported and may bedropped while being transported.

After water and fibres addition, homogenization by mixing or blendingand pouring into place, it is advantageous for the concrete to undergo aperiod of cure, preferably in a humid atmosphere. Next, it is desirableto subject the concrete to an heat treatment under controlledatmosphere. This heat treatment under controlled atmosphere may takeplace at a temperature of between 80° C. and 600° C., preferably between110° C. and 350° C. Of course, the heat-treatment under controlledatmosphere temperature is chosen taking into account the nature of thefibres, so as not to damage them.

A concrete is thus obtained which possesses good mechanical properties,although it has been prepared in a relatively simple manner, has a lowcement content and has not undergone compacting operation.

The impact or shock protection properties are manifested by an abilityto resist fracture or shattering under impact or shock.

The projectile protection properties are manifested by an ability toslow and stop penetration of this projectile and to resist fracture orshattering under impact of projectile. In other words, a concretepossessing good projectile protection properties is a concrete which hasa projectile penetration resistance sufficiently high for the depth ofpenetration of this projectile to be small and which, furthermore doesnot break under impact of projectile.

The concrete according to the invention therefore enables to reachimportant impact, shock or projectile protection even when it isemployed in the form of thin slabs, walls or partitions.

It may therefore be employed for providing coatings for protectionagainst small size projectiles, such as bullets fired by firearms, oragainst large projectiles, such as bombs.

It may also serve for manufacturing personal or collective shelters,whether static or mobile, for the protection of banks, prisons andso-called vital industrial installations, against intrusions or attackswhich could be committed, in particular using pick hammers or similartools, or for coating objects which have to be transported and may bedropped while being transported.

It may furthermore be used in the nuclear field or for earthquakeprotection.

PREPARATION OF THE CONCRETE ACCORDING TO THE INVENTION

The concrete according to the invention may be prepared in the followingmanner:

constituents a), b), c), d) and f) are put into a mixer and mixed untilthe desired consistency is obtained,

then fibres e) are added while continuing to mix, so that the fibres aredispersed as uniformly as possible,

next, the mix obtained is casted into a mould which is vibrated,

after 2 to 10 minutes, vibration is stopped and the mould and its mixare left to stand for about 24 hours,

the concrete is then removed from the mould and preferably left to standfor at least one day, advantageously in a humid atmosphere (moisturecontent greater than about 65% relative humidity),

after which, the concrete is preferably subjected to an heat treatmentunder controlled atmosphere at a temperature of between about 80° C. andabout 600° C., preferably between about 110° C. and about 350° C., untilit is dry, which means for those skilled in the art that it has afree-water content of generally less than 0.2% as a percentage by weightwith respect to the concrete.

EXAMPLES

Concretes were prepared by the process described above using thecompositions indicated in Table A below, in which:

composition A1 corresponds to Example No. 9 of French Patent ApplicationNo. 2,633,922, and

composition A2 corresponds to Example No. 3 of French Patent ApplicationNo. 2,640,962.

                                      TABLE A                                     __________________________________________________________________________            CONCRETES TESTED                                                      Constituents                                                                          Example 1                                                                              Example 2                                                                              Example 3                                                                              Example 4                                                                              A1       A2                       __________________________________________________________________________    Particles (A) and                                                                     81% tabular-form                                                                       50.6% of ALAG ®                                                                    80% of brown                                                                           86% of brown                                                                           35.5% of 0/6                                                                           50.0% of fine grit,      their size                                                                            alumina  0.5 to 5 mm,                                                                           corundum corundum,         300-1000 mm                      0.01 to 5 mm                                                                           32.8% of brown                                                                         0.01 to 5 mm                                                                           0.01 to 5 mm                                                                           49.3% of 6/10                                                                          6.4% of C 600                                                                 quartz                                    corundum                   diorite  8.4% of C 400                                                                 quartz                                    0.01 to 0.5 mm                                               Particles (B) and                                                                     5% of silica fume                                                                      5.9% of silica fume                                                                    3.5% of silica fume                                                                    5% of silica fume                                                                      1.4% of silica                                                                         3.5% of microsilica      their size                                                                            100 Å to 1 μm                                                                   100 Å to 1 μm                                                                   100 Å to 1 μm                                                                   100 Å to μm                         Particles (C) and                                                                     10% of fine alumina                                                                    5.9% of fine alum-                                                                     --       5% of fine alumina,                                                                    --                                their size                                                                            1 to 10 μm                                                                          ina 1 to 10 μm 1 to 10 μm                              Cement  4% of alumina                                                                          4.8% of alumina                                                                        16.5% of CPA 55                                                                        4% of alumina                                                                          13.8% of HP                                                                            31.7% of CPA 55                  cement   cement            cement   cement                            Dispersing                                                                            0.08% of TPP                                                                           0.09% of TPP                                                                           0.35% of PNS                                                                           0.08% of TPP                                                                           0.28% of Sikafluid                                                                     1.4%                     agent(s).sup.(1)                                                                      0.03% of PNS                                                                           0.035% of PNS     0.03% of PNS                               Admixture.sup.(2)                                                                     0.01% of citric acid                                                                   0.01% of citric acid                                                                   --       0.01% of citric acid                                                                   --       0.03% of anti-foam                                                            agent                    Fibres and type.sup.(3)                                                               80 kg/m.sup.3, i.e. 2.5%                                                               80 kg/m.sup.3, i.e. 2.5%                                                               80 kg/m.sup.3, i.e. 2.5%                                                               80 kg/m.sup.3, i.e. 2.5%,                                                              80 kg/m.sup.3, i.e.                                                                    11%%                             steel    steel    steel    steel    cast iron                                                                              metal                    Water.sup.(4)                                                                         3.6%     3.2%     3.5%     3.6%     3.9%     9.2%                     Rest period after                                                                     >1 day in a humid                                                                      >1 day in a humid                                                                      >1 day in a humid                                                                      >1 day in a humid                                                                      --       >1 day in a humid        demoulding                                                                            atmosphere                                                                             atmosphere                                                                             atmosphere                                                                             atmosphere        atmosphere               Heat treatment                                                                        At 280° C.                                                                      At 280° C.                                                                      At 280° C.                                                                      At 280° C.                                                                      --       At 200° C.                                                    (compacted)                       __________________________________________________________________________     .sup.(1) TPP: sodium tripolyphosphate sold by the RhonePoulenc company        PNS: sodium polynaphthalene sulphonate sold by the C.F.P.I. company under     the name "GALORYL PA 120                                                      .sup.(2) The weight percentage of admixture was calculated with respect t     the weight of particles (A), (B), (C), of cement and of dispersing agent.     .sup.(3) The fibres used were straight smooth steel fibres having a lengt     of about 17 mm and a diameter of about 0.2 mm sold by the Trefileries de      Conflandey company.                                                           .sup.(4) The percentage of water was also calculated with respect to the      weight of particles (A), (B), (C), of cement and of dispersing agent.    

The mechanical properties of the concretes according to the inventionwere measured on test pieces (64×54×230 mm) after heat treatment undercontrolled atmosphere during 48 hours. The results are collated in TableB below in which the following are also given:

the mechanical properties of concretes A1 and A2, as indicated in FrenchPatent Applications Nos. 2,633,922 and 2,640,962, respectively,

as well as the results of the penetration resistance tests on theconcretes according to the invention.

The measurements of the compression strength and flexural strength ofthe concretes according to the invention were carried out according tothe European Recommendation No. PRE R27.

The measurements of porosity of the concretes according to the inventionwere carried out according to the NF B40.321 standard.

The penetration resistance tests were carried out on slabs made ofconcrete according to the invention used as targets with dimensions ofabout 40×40×10 cm. The projectiles were ordinary 12.7 mm-diameterbullets weighing about 46 g, fired using a 12.7-calibre machine gun. Thedistance separating the end of the 12.7-calibre gun from the targets wassuch that the bullets reached the targets with a velocity of the orderof 830 m/s.

Next, the depth of penetration was measured on the targets which hadwithstood the impact of the projectile, by inserting a gauge into theimprint left by the projectile after recochet on surface of theconcrete.

                                      TABLE B                                     __________________________________________________________________________    RESULTS      Example 1                                                                          Example 2     Example 3                                                                          Example 4     A1 A2                      __________________________________________________________________________    Compression strength, in MPa                                                               170  230           180  150           -- 205                     Flexural strength,                                                                         26   26            22   18            13.2                                                                             30.8                    in MPa                                                                        Porosity, in %                                                                             12   9             10   14            -- --                      Depth of penetration of the                                                                12 mm                                                                              .sup.(1) 60 mm with cracking in                                                             25 mm                                                                              .sup.(2) 40 mm in concrete                                                                  --at-                                                                            --                      projectile        concrete not heat-treated and                                                                    treated at 80° C. and 17 mm                                            in                                                         19 mm without cracking in heat-                                                                  concrete heat-treated at 280°                                          C.                                                         treated concrete                                            __________________________________________________________________________     .sup.(1) The tests were carried out both on concrete heattreated under        controlled atmosphere at 280° C. and on concrete not heattreated       .sup.(2) The tests were carried out both on concrete heattreated under        controlled atmosphere at 80° C. and on concrete heattreated at         280° C. under controlled atmosphere                               

It is surprising to note that the concretes of Examples 1 to 3 have aflexural strength almost twice as high as that of concrete A1 which is,however a compacted concrete.

Furthermore, flexural strength of the concrete of Example 3 is barely28.6% less than that of concrete A2, although concrete A2 has a cementcontent almost twice as high, a fibres content four times greater andparticles (A) having a greater hardness than that of particles (A) ofthe concrete of Example 3.

With regard to the projectile penetration resistance, it was establishedthat all the projectiles were stopped by the concretes according to theinvention and that targets remained in one piece and did not crack.

The heat-treated under controlled atmosphere concretes show a greaterpenetration resistance than the non-heat-treated concretes.

In addition, penetration resistance tests carried out using 12.7mm-calibre piercing-tip (PPI) bullets have shown that the concretes ofExamples 1 and 4 stop this type of projectile. This is surprising whenit is recalled that these same projectiles will pierce a 27 mm layer ofarmour steel.

Other tests were carried out using several kinds of projectiles. Thecompositions of the concretes tested are given in Table C below. Thecharacteristics (mechanical properties and porosity) are given in TableD.

                  TABLE C                                                         ______________________________________                                                 CONCRETES TESTED                                                     Constituents                                                                             Example 5      Ordinary concrete                                   ______________________________________                                        Particles (A)                                                                            86% of brown corundum,                                                                       32% of 10/20 mm gravel                              and their size                                                                           0.01 to 10 mm  14% of 5/10 mm gravel                                                         38% of 0/5 mm sand                                  Particles (B)                                                                            5% of silica fume,                                                                           --                                                  and their size                                                                           100 Å to 1 μm                                               Particles (C)                                                                            5% of fine alumina,                                                                          --                                                  and their size                                                                           1 to 10 μm                                                      Cement     4% of alumina cement                                                                         15% of CPA 55                                       Dispersing 0.08% of TPP   1% of PMS                                           agents(s).sup.(1)                                                                        003% of PNS                                                        Admixture  0.01% of citric acid                                                                         --                                                  Fibres and type.sup.(2)                                                                  80 kg/m.sup.3, --                                                             i.e. 2.5% steel                                                    Water.sup.(2)                                                                            3.6%           7.5%                                                Heat treatment                                                                           At 280° C.                                                                            --                                                  Rest period                                                                              >1 day in a    --                                                             humid atmosphere                                                   ______________________________________                                         .sup.(1) TPP and PNS: as in Table A                                           PMS: polymelamine sulphonate sold under the name "Resin GT" by the Chryso     company                                                                       .sup.(2) As in Table A                                                   

                  TABLE D                                                         ______________________________________                                        CHARACTERISTICS   Example 5                                                                              Ordinary concrete                                  ______________________________________                                        Compression strength, in MPa                                                                    150      45                                                 Flexural strength, in MPa                                                                       18       --                                                 Porosity in %     14       --                                                 ______________________________________                                    

OTHER TESTS

a) 1:5 scale 1000-pound bombs:

The targets were blocks having a size of 1×1.25×1 m, composed of a first20 cm-thick layer of concrete according to Example 5 in contact with asecond 80 cm-thick layer of ordinary concrete.

The projectiles reached the targets (the first layer) with a velocity ofabout 270 m/s.

The depth of penetration of the projectiles remained less than 30 mm.The projectiles were virtually broken up by impact and no cracking ofthe targets was observed.

b) 1:2 scale 1000-pound bombs:

The targets were blocks having a size of 2×2×1.2 m, composed of a first50 cm-thick layer of concrete according to Example 5 in contact with asecond 70 cm-thick layer of ordinary concrete.

The projectiles reached the targets (the first layer) with a velocity ofabout 280 m/s.

The depth of penetration of the projectiles remained less than 40 cm.

During one test carried out under the same conditions using a slabconsisting entirely of ordinary concrete, the depth of penetration ofthe projectiles was about 90 cm.

c) 14.5 mm-calibre API projectiles

The targets were slabs made of the concrete of Example 5, having a sizeof 2×3×0.2 m the rear face of which was covered with a 10 mm-thickreinforcing plate of mild steel.

The projectiles reached the targets with a velocity of about 980 m/s.

The depth of penetration of the projectiles remained less than 100 mm.After firing 7 times in succession at the same slab, aiming at the sameimpact point, the depth of penetration was still less than 160 mm.

Clearly, the invention is in no way limited by the particular featureswhich have been specified in the foregoing or by the details of theexamples chosen to illustrate it. Many modifications may be made to theparticular embodiments and to the examples which have been described byway of illustration and to their constituent components without therebydeparting from the scope of the invention. The latter consequentlyencompasses all means that are technical equivalents of the meansdescribed, as well as the combination thereof.

We claim:
 1. An impact resistant concrete composition containing anadmixture of a hydraulic binder, aggregates, and fibers, saidcomposition comprising:a) from 70 to 86% of particles (A) having aparticle size distribution which ranges from a minimum size of 0.01 mmup to a maximum size of 3-50 mm, b) from 2 to 10% of particles (B)having a particle size of between 0.01 and 1 μm, c) from 3 to 20% ofhydraulic binder, d) from 0.1 to 3% of a dispersant or of a plasticizer,e) from 0.05 to 8.5% of fibers, and f) mixing water, the percentage ofall being percentages by weight relative to the sum of the weights ofconstituents a) to d).
 2. The concrete composition according to claim 1,wherein the particles (A) are aggregates having a hardness greater than5 Mohs.
 3. The concrete composition- according to claim 2, wherein theparticles (A) are selected from the group consisting of tabular-formalumina, electrofused corundum, natural or calcined bauxite,alumina-based materials, granite, quartzite, diabase, basalt,crystalline quartz, silicon carbides, silicon nitrides, boron carbides,titanium carbides, metals, metal alloys and mixtures thereof.
 4. Theconcrete composition according to claim 1, wherein the particles (B) areselected from the group consisting of fly ashes and ultra-fine fillersselected from the group consisting of ultra-fine silica fume, ultra-finemicrosilicas, ultra-fine kaolinites, ultra-fine calcined clays,ultra-fine limestone fines, ultra-fine chromium oxide, ultra-finetitanium oxide, ultra-fine zirconium oxide, ultra-fine aluminum oxide,and mixtures thereof.
 5. The concrete composition according to claim 1,wherein the hydraulic binder is selected from a group consisting of: analumina cement, a mixture of alumina cements, Portland cement, avitreous cement, a mixture of vitreous cements, a mixture of at leastone alumina cement with at least one Portland cement, a mixture of atleast one vitreous cement with at least one Portland cement, a cementcontaining slag, a cement containing pozzolanes and a mixture thereof.6. The concrete composition according to claim 5, wherein when thehydraulic binder is a Portland cement, its content is between about 10and 20%, and when the hydraulic binder is an alumina cement or avitreous cement, its content is between 3 and about 10%.
 7. The concretecomposition according to claim 1, wherein the fibers are metal fibers,mineral fibers, glass fibers, carbon fibers, plastic material fibers ora mixture of these fibers.
 8. The concrete composition according toclaim 7, wherein the fibers are metal fibers.
 9. The concretecomposition according to claim 1, wherein the fiber content is between0.05 and 5%.
 10. The concrete composition according to claim 1, whereinit further comprises: particles (C) having, a particle size of between 1and 10 μm.
 11. The concrete composition according to claim 10 whereinthe particles (C) content is legs than 12% by weight with respect to thesum of the weights of constituent a) to d) and of the weight of saidparticles (C), the percentage of fibers then being calculated by weightwith respect to the sum of the weights of constituents a) to d) and ofthe weight of said particles (C).
 12. The concrete composition accordingto claim 10, wherein particles (C) are selected from the groupconsisting of tabular-form alumina, electrofused corundum, natural orcalcined bauxite, alumina-based materials, granite, limestones,quartzite, diabase, basalt, ground crystalline quartz, silicon carbides,silicon nitrides, boron carbides, titanium carbides, metals, metalalloys and mixtures thereof.
 13. The concrete composition according toclaim 10, wherein the composition further comprises one or moreadditional components selected from the group consisting of anti-foamagents, water-proofing agents, air entrainers, set-accelerators,set-retarder, colorants and mixtures thereof.
 14. The concretecomposition according to claim 1, wherein the mixing water is present inan amount between 2 to 5% by weight relative to the sum of the weightsof constituents a) to d) of the concrete composition.
 15. A method forpreparing an impact resistant concrete composition, which contains anadmixture of a hydraulic binder, aggregates, and metal fibers, saidcomposition comprising:a) from 70 to 86% of particles (A) having aparticle size distribution which ranges from 0.01-3 mm to 0.01-50 mm, b)from 2 to 10% of particles (B) having particle size of between 0.01 and1 μm, c) from 0 to 12% of particles (C), wherein the majority of theparticles are of the size between 1 and 10 μm, d) from 3 to 20% ofhydraulic binder, e) from 0.1 to 3% of a dispersant or of a plasticizer,f) from 0.05 to 8.5% of fibers, and g) from 2 to 5% of water, thepercentage of all being percentages by weight relative to the sum of theweights of constituents a) to e), the method comprising the steps of:mixing the particles (A), the particles (B), the particles (C), thehydraulic binder, the dispersant or plasticizer, and the water to form amix; adding and uniformly dispersing the fibers in the mix; and, castingthe mix into a mold.
 16. The method according to claim 15, wherein thecomposition is subjected to setting and hardening.
 17. The methodaccording to claim 15, wherein the concrete composition is subjected toheat treatment under controlled atmosphere.
 18. The method according toclaim 15, wherein the heat treatment under controlled atmosphere iscarried out at a temperature of between 80° C. and 600° C.
 19. A methodfor using a shield against impacts or shocks which comprises providingthe shield with a concrete composition according to claim 1, wherein thecomposition forms a wall that resists fracture or shattering fromimpacts or shocks.
 20. A method for using a protection shielding againstprojectiles which comprises providing a concrete composition accordingto claim 1, wherein the composition forms at least part of the shieldingto slow and stop the penetration of the projectiles.
 21. A method forusing a protection shielding against projectiles according to claim 20,wherein the projectiles include projectiles fired by a 12.7-calibermachine gun, 14.5 mm projectiles, 1:5 scale 1000-pound bombs, or 1:2scale 1000-pound bombs.
 22. A method for using a shield against impactsor shocks which comprises providing the shield with a concretecomposition according to claim 1, wherein the composition forms platesor slabs having a reinforcing plate on their rear face.
 23. The methodaccording to claim 15, wherein the heat treatment under controlledatmosphere is carried out at a temperature of between 110° C. and 350°C.
 24. The concrete composition according to claim 13, wherein thecontent of the additional components is less than 1% by weight withrespect to the sum of the weights of constituents a) to d) of theconcrete plus the weight of particles (C).
 25. The method according toclaim 15, wherein composition has a compressive strength of 150-230 MPa.